Diastereoselective catalytic hydrogenation of pyruvic acid esters, amides, and their Schiff bases has been well studied over a long period to show that proline is one of the most effective chiral auxiliaries. Proline derivatives have been used as auxiliaries in the diastereoselective catalytic hydrogenation of pyruvamide Schiff bases. The diastereoselective hydrogenation resulted in up to a 78% enantiomeric excess of the amino acid derived from the hydrolysis of the dipeptide products. The chelation hypothesis explains the stereochemistry of the catalytic hydrogenation using (S)-proline esters in the amide moiety and the two chiral centers in the amide and Schiff base moieties.

N-t-Butyloxycarbonyl-amino acids (Boc-) are labile on heating to afford free amino acids, but Boc-aspartic acid gives a kind of polypeptide.This chemical feature of Boc-aspartic acid may be caused by dehydration between two carboxyl groups as well as the formation of a free amino group.Boc-Asparagine may have a similar reactivity to Boc-aspartic acid.This research describes polypeptide formation by heating Boc-asparagine and its isomer Boc-aspartic acid amide.

An acid labile N-protecting group for amino acids, t-butyloxycarbonyl (Boc) group has deprotected at elevated temperatures. The study describes an application of the lability on heating to synthesis of polypeptides from acidic amino acids. t-Butyloxycarbonyl-acidic amino acids (aspartic acid, glutamic acid and beta-aminoglutaric acid) and their anhydrides were heated at the higher temperatures than their melting points. Anhydrides of t-butyloxycarbonyl-aspartic acid and t-butyloxycarbonyl-beta-aminoglutaric acid gave polypeptides. Thermal analyses of the substrates clarified the pathway of the polypeptide formation.

Malic acid, a component present in fruit, is known to be an important precursor for the prebiotic formation of polyaspartic acid. Malic acid is a dicarboxylic acid, possessing one hydroxyl group. It yields many types of crystalline salts with amino compounds. Although the thermal reactions of the amino salts have been reported, their dehydration reaction pathway has not been studied. This paper describes the dehydration process using thermal gravimetry and differential thermal analysis. The results show that the malic acid monobenzylamine and the dibenzylamine salts release water molecules during an endothermic reaction to afford malic acid benzylimide and malic acid dibenzylamide, respectively. The latter compound is stable up to 230 degrees C.

A jet of nitrogen plasma blown into a sodium carbonate solution produced reductive fixation of carbonate to formate. The reaction is explained by the nitrogen-mediated oxidation-reduction of water.

Aspartic acid is one of the proteinaceous acidic amino acids, has two carboxyl groups per molecule. Together, these two different carboxyl groups play an important role in thermal reactions. When aspartic acid is heated at elevated temperatures (up to 400 degrees C), it polymerizes to form polyaspartic acid. This reaction does not proceed on heating glutamic acid, which is another acidic amino acid. Present research used both thermal analysis and infrared measurements to examine the heating behaviour of aspartic acid over a given time period. The measurements reveal some aspects of the thermal reaction mechanism. During the heating reactions, amide bonds gradually form and then imide bond formation follows. This work may be useful for clarifying the mechanism of thermal polycondensation of aspartic acid and the structural features of the products.

Diastereomer resolution by high performance liquid chromatography (HPLC) has been useful for determining the correlation between molecular structure and hydrophobicity. Three pairs of diastereomeric tartaric acid monoamides (O,O'-diacetyl-(2R, 3R)-tartaric amides) are resolved into each diastereomer by achiral reversed-phase HPLC (RP-HPLC). There are some correlations between the molecular structure and the elution order of the diastereomers. O,O'-Diacetyl-(2R,3R)-tartaric acid (R)-amides ((R,R,R)-tartaramides) are eluted faster than (R,R,S)-tartaramides. H-1 NMR spectra of these compounds in acetonitrile-d(3) (CD3CN) shows that the dihedral angle is about 110 degrees around the vicinal protons of the tartaric acid moiety. When we adopt this value for calculation of the molecular structure, the logarithm of the partition coefficient (log P value) of tanaramides in n-octanol per water explains the elution order of diastereomers. The findings play a role in both determination of the elution order and the conformation of similar chiral compounds in RP-HPLC.

Plasma-jet in aqueous solutions is known to disproportionate water to give hydrogen and hydroxyl radicals. Maleic acid, which is a carbon carbon double bond bearing dicarboxylic acid, underwent addition of hydrogen, hydrogen plus hydroxyl, hydroxyl species under an argon hydrogen plasma-jet. Maleic acid (10mM) yielded 42% succinic acid (dihydrogenated product) under an argon-hydrogen (1.5 and 0.5 L min(-1)) plasma-jet. This demonstrates an effective reduction method for maleic acid by plasma-jet in aqueous solutions.

Introduction of argon-are plasma into an aqueous solution of formic acid resulted in the formation of oxalic acid. The reaction conditions for the dimerization were studied. The maximum yield of oxalic acid reached 47-50% when the reaction was carried out using sodium formate or calcium formate. Dimerization of acetic acid was also examined.

Polycyclic aromatic hydrocarbons (PAHs) are one of the most ubiquitous organic compounds in the universe. PAHs are sometimes used as a molecular marker for biological activity, however, they are also formed by abiogenic processes. Carbon isotopic compositions of individual PAHs have important clues to clarify their origins and formation mechanisms for the better understanding in organic cosmogeochemistry of PAHs. In the Asuka-881458 carbonaceous chondrite which was recovered from Antarctica in 1989, more than 70 PAHs were identified from naphthalene to benzo(ghi)perylene, where fluoranthene and pyrene are the most abundant. Carbon isotopic compositions of individual PAHs range from −26 to 8‰ (relative to PDB). More condensed PAHs are more depleted in 13C as the H/C ratio decreases. The carbon isotope distribution of PAHs containing more than three rings is similar to that from the Murchison meteorite, but clearly different from that of the terrestrial PAHs. The isotope distribution suggests that the PAHs in carbonaceous chondrites are formed under kinetic control rather than by thermodynamic equilibrium. In particular, two reaction pathways (‘pyrene series’ and ‘fluoranthene series’) can be distinguished assuming kinetic control. The relatively large isotopic fractionation could occur during cyclization and/or carbon addition in the interstellar or meteorite parent body environment.